This invention relates to a gas-insulated switchgear (GIS) of an 1xc2xd CB system and, more particularly to its connecting line arrangement for supplying or transmitting and receiving electric power.
A conventional construction of an 1xc2xd CB system gas-insulated switchgear is shown in FIGS. 9-11. FIG. 9 is an electric circuit for a transformer station and shows a single line connection diagram for one diameter. FIG. 10 is a plane view of a gas-insulated switchgear which has the electric circuit shown in FIG. 9, and FIG. 11 is a front view of the gas-insulated switchgear in FIG. 10. The gas-insulated switchgear comprises three circuit breakers CB1, CB2 and CB3 between main buses 1 and 2, disconnecting switches DS connected to both sides of each of the circuit breakers, and a current transformer and ground switches each not shown, and electric power is received from and supplied to terminals (bushing, cable head) of connecting lines 5, 6 led out from between the disconnecting switches.
Those conventional gas-insulated switchgears are disclosed in JP A 57-202808, Japanese Utility-model Laid-open Application No. 60-141606, JP A 11-146522, JP A 2000-50436, etc., each of which proposes a compact construction or a construction that maintenance and inspection can be easily performed, of the gas-insulated switchgear.
In the above-mentioned 1xc2xd CB system gas-insulated switchgear, the connecting lines for transmitting and receiving electric power are led out from between the two circuit breakers in view of reliability. Since the circuit breakers each are large in size and high in cost, a volume ratio and a cost ratio occupied by the 1xc2xd CB system gas-insulated switchgear become large. Under such a condition, a system of gas-insulated switchgear is required which is able to increase only the number of connecting lines without increasing the number of circuit breakers.
An object of the invention is to provide a gas-insulated switchgear which has connecting lines for supplying and receiving electric power, the number of which is increased without increasing the installation number of circuit breakers and the installation area of the gas-insulated switchgear, in view of the problems in the above-mentioned conventional gas-insulated switchgears.
The present invention to attain the above object is resides in a gas-insulated switchgear of an 1xc2xd CB system, in which three circuit breakers are electrically connected in series between a pair of buses and a connecting line for supplying and receiving electric power is led out from between the circuit breakers, and which is characterized in that the gas-insulated switchgear is constructed so that a further connecting line for supplying and receiving electric power is directly led out from the bus through a disconnecting switch.
According to an aspect of the present invention, a leading out point of the above-mentioned further connecting line is the bus in a diameter end portion.
According to another aspect of the present invention, a leading out point of the above-mentioned further connecting line is the bus in a diameter which is an end portion of the gas-insulated switchgear. In this case, the above-mentioned buses each are a three phase package bus having three phase conductors shaped in triangle with an apex at a lateral or horizontal side, and when other conductors are connected vertically to the above-mentioned three phase conductors, they are connected after at least one of vertically overlapped two conductors of the three phase conductors is extended to separate horizontally the three phase conductors from each other.
This construction can be made more compact than in the first aspect because the whole construction of the gas-insulated switchgear provided with a new connecting line does not change, compared with that before provision of the new connecting line.
Further, in the case where the further connecting lines are led out from both of the buses, they are led out in the same directions from the same end portions of the buses.
(Note: A bay is a generic term of one circuit corresponding to one circuit breaker, and three bays incorporated make one diameter. An 1xc2xd CB system is a system in which two circuits are incorporated in one diameter (=3CB bays), that is, it is an (3CB 2=) 1xc2xd CB system.)